Many synthetic nitrofurans and imidazole compounds are being used as chemotherapeutic agents or antibacterial food additives. Our previous studies with nitrofurans have shown that a chemotherapeutic agent, a food additive, an antischistosomal agent and an antitrichomoniasis agent are mutagenic in Neurospora crassa. Our studies also show that a NO2 group at the C5 position and a particular side chain at the C2 position are necessary for the mutagenic activity of nitrofurans. It would be of interest to determine whether other chemotherapeutic agents are mutagenic in N. crassa, to verify function-structure relationship of nitrofurans and imidazole compounds and to determine the type of genetic alterations caused by chemotherapeutic agents. The ad-3 test system of N. crassa developed by F. J. de Serres is used in this study. Conidia are treated with chemicals in pH 7 buffer at 30 degrees C for 2 hours. At the end of the treatment, chemicals are decanted and conidia are washed by centrifugation. The treated and untreated conidia are assayed for the presence of ad-3 mutants by the direct method. The isolated mutants are tested for genotype, complementation pattern and spectra of genetic alterations.